Tear resistant flex circuit assembly

ABSTRACT

A medical device for sympathetic nerve ablation may include a catheter shaft, an expandable member disposed on or coupled to the catheter shaft, and a plurality of elongate electrode assemblies each constructed as a flexible circuit having a plurality of layers. The expandable member may be configured to shift between an unexpanded configuration and an expanded configuration. The plurality of electrode assemblies may be disposed on an outer surface of the expandable member. Each of the plurality of electrode assemblies may include enhanced tear resistance properties such as through the inclusion of a reinforcement structure with one or more of the layers of the electrode assemblies.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119 to U.S. Provisional Application Ser. No. 61/924,113, filed Jan. 6, 2014, the entirety of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure pertains to medical devices, and methods for manufacturing medical devices. More particularly, the present disclosure pertains to flexible circuits including ablation electrodes having enhanced tear resistance.

BACKGROUND

A wide variety of intracorporeal medical devices have been developed for medical use, for example, intravascular use. One such medical device is an ablation catheter configured for tissue ablation, such as sympathetic nerve ablation. The medical device may include one or more electrode assemblies constructed as flexible circuits mounted on an inflatable balloon. In some instances, it has been observed that the flexible circuits may catch on the edge of a guide catheter through which the ablation catheter is positioned when proximally retracting the ablation catheter into the guide catheter.

Accordingly, it may be desirable to provide an electrode assembly formed as a flexible circuit that includes structural features that may reduce the likelihood of tearing in the event the electrode assembly catches on the end of a guide catheter (or other device) when being retracted, for example, into the guide catheter.

BRIEF SUMMARY

The disclosure is directed to several alternative designs, materials and methods of manufacturing medical device structures and assemblies, and uses thereof.

Accordingly, one illustrative embodiment is a medical device for sympathetic nerve ablation. The medical device includes a catheter shaft having a longitudinal axis and an expandable balloon disposed on the catheter shaft. The balloon is capable of shifting between an unexpanded configuration and an expanded configuration. The medical device further includes an elongate electrode assembly constructed as a flexible circuit having a plurality of layers. The electrode assembly is mounted on an outer surface of the balloon. The flexible circuit includes a first layer that has an initial tear strength of greater than 7.5 N (1.7 lbf) according to ASTM D-1004-09. In some instances, the first layer may have a tear propagation strength of greater than 0.15 N (0.03 lbf) according to ASTM D-1922-09.

Another illustrative embodiment is a medical device for tissue ablation. The medical device includes a catheter shaft having a longitudinal axis and an expandable member coupled to the catheter shaft. The expandable member is capable of shifting between an unexpanded configuration and an expanded configuration. The medical device further includes an elongate electrode assembly constructed as a flexible circuit mounted on an outer surface of the expandable member. The flexible circuit includes a plurality of conductive traces interposed between a first insulating layer formed of a reinforced polymeric material and a second insulating layer formed of a polymeric material.

Yet another illustrative embodiment is a method of forming a medical device for tissue ablation. The method includes providing an electrode assembly constructed as a flexible circuit having a plurality of conductive traces interposed between a first insulating layer formed of a reinforced polymeric material and a second insulating layer formed of a polymeric material. The formed flexible circuit is then mounted onto an outer surface of an inflatable balloon of a balloon catheter.

The above summary of some embodiments is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The Figures, and Detailed Description, which follow, more particularly exemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be more completely understood in consideration of the following detailed description in connection with the accompanying drawings, in which:

FIG. 1 is a schematic view of an example sympathetic nerve ablation device;

FIG. 2 is a perspective view of an example expandable member of a sympathetic nerve ablation device;

FIG. 3 is a partial top view of the expandable member of FIG. 2 in an unrolled or flat configuration;

FIG. 4 is a bottom view of a portion of an exemplary electrode assembly;

FIG. 5 is a cross-sectional view of the exemplary electrode assembly of FIG. 4 taken along line 5-5 of FIG. 4;

FIG. 6 is an exploded view of the exemplary electrode assembly of FIG. 4;

FIG. 7 is a schematic view of a reinforcement layer of an exemplary electrode assembly mounted on an expandable member;

FIG. 8A is a schematic view of another reinforcement layer of an exemplary electrode assembly mounted on an expandable member;

FIG. 8B is a schematic view of another reinforcement layer of an exemplary electrode assembly mounted on an expandable member;

FIG. 9 is a schematic view of another reinforcement layer of an exemplary electrode assembly mounted on an expandable member;

FIG. 10 is a schematic view of another reinforcement layer of an exemplary electrode assembly mounted on an expandable member; and

FIG. 11 is a cross-sectional view of an exemplary electrode assembly including a reinforcement layer.

While the disclosure is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure.

DETAILED DESCRIPTION

The following description should be read with reference to the drawings, which are not necessarily to scale, wherein like reference numerals indicate like elements throughout the several views. The detailed description and drawings are intended to illustrate but not limit the claimed invention. Those skilled in the art will recognize that the various elements described and/or shown may be arranged in various combinations and configurations without departing from the scope of the disclosure. The detailed description and drawings illustrate example embodiments of the claimed invention.

For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification.

All numeric values are herein assumed to be modified by the term “about,” whether or not explicitly indicated. The term “about”, in the context of numeric values, generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (i.e., having the same function or result). In many instances, the term “about” may include numbers that are rounded to the nearest significant figure. Other uses of the term “about” (i.e., in a context other than numeric values) may be assumed to have their ordinary and customary definition(s), as understood from and consistent with the context of the specification, unless otherwise specified.

The recitation of numerical ranges by endpoints includes all numbers within that range, including the endpoints (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).

As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.

It is noted that references in the specification to “an embodiment”, “some embodiments”, “other embodiments”, etc., indicate that the embodiment(s) described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it would be within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments, whether or not explicitly described, unless clearly stated to the contrary. That is, the various individual elements described below, even if not explicitly shown in a particular combination, are nevertheless contemplated as being combinable or arrangable with each other to form other additional embodiments or to complement and/or enrich the described embodiment(s), as would be understood by one of ordinary skill in the art.

Certain treatments are aimed at the temporary or permanent interruption or modification of select nerve function. In some embodiments, the nerves may be sympathetic nerves. One example treatment is renal nerve ablation, which is sometimes used to treat conditions such as or related to hypertension, congestive heart failure, diabetes, or other conditions impacted by high blood pressure or salt retention. The kidneys produce a sympathetic response, which may increase the undesired retention of water and/or sodium. The result of the sympathetic response, for example, may be an increase in blood pressure. Ablating some of the nerves running to the kidneys (e.g., disposed adjacent to or otherwise along the renal arteries) may reduce or eliminate this sympathetic response, which may provide a corresponding reduction in the associated undesired symptoms (e.g., a reduction in blood pressure).

Some embodiments of the present disclosure relate to a power generating and control apparatus, often for the treatment of targeted tissue in order to achieve a therapeutic effect. In some embodiments, the target tissue is tissue containing or proximate to nerves. In other embodiments, the target tissue is sympathetic nerves, including, for example, sympathetic nerves disposed adjacent to blood vessels. In still other embodiments the target tissue is luminal tissue, which may further comprise diseased tissue such as that found in arterial disease.

In some embodiments of the present disclosure, the ability to deliver energy in a targeted dosage may be used for nerve tissue in order to achieve beneficial biologic responses. For example, chronic pain, urologic dysfunction, hypertension, and a wide variety of other persistent conditions are known to be affected through the operation of nervous tissue. For example, it is known that chronic hypertension that may not be responsive to medication may be improved or eliminated by disabling excessive nerve activity proximate to the renal arteries. It is also known that nervous tissue does not naturally possess regenerative characteristics. Therefore it may be possible to beneficially affect excessive nerve activity by disrupting the conductive pathway of the nervous tissue. When disrupting nerve conductive pathways, it is particularly advantageous to avoid damage to neighboring nerves or organ tissue. The ability to direct and control energy dosage is well-suited to the treatment of nerve tissue. Whether in a heating or ablating energy dosage, the precise control of energy delivery as described and disclosed herein may be directed to the nerve tissue. Moreover, directed application of energy may suffice to target a nerve without the need to be in exact contact, as would be required when using a typical ablation probe. For example, eccentric heating may be applied at a temperature high enough to denature nerve tissue without causing ablation and without requiring the piercing of luminal tissue. However, it may also be desirable to configure the energy delivery surface of the present disclosure to pierce tissue and deliver ablating energy similar to an ablation probe with the exact energy dosage being controlled by a power control and generation apparatus.

In some embodiments, efficacy of the denervation treatment can be assessed by measurement before, during, and/or after the treatment to tailor one or more parameters of the treatment to the particular patient or to identify the need for additional treatments. For instance, a denervation system may include functionality for assessing whether a treatment has caused or is causing a reduction in neural activity in a target or proximate tissue, which may provide feedback for adjusting parameters of the treatment or indicate the necessity for additional treatments.

Many of the devices and methods described herein are discussed relative to renal nerve ablation and/or modulation. However, it is contemplated that the devices and methods may be used in other treatment locations and/or applications where sympathetic nerve modulation and/or other tissue modulation including heating, activation, blocking, disrupting, or ablation are desired, such as, but not limited to: blood vessels, urinary vessels, or in other tissues via trocar and cannula access. For example, the devices and methods described herein can be applied to hyperplastic tissue ablation, cardiac ablation, pain management, pulmonary vein isolation, pulmonary vein ablation, tumor ablation, benign prostatic hyperplasia therapy, nerve excitation or blocking or ablation, modulation of muscle activity, hyperthermia or other warming of tissues, etc. The disclosed methods and apparatus can be applied to any relevant medical procedure, involving both human and non-human subjects. The term modulation refers to ablation and other techniques that may alter the function of affected nerves and other tissue.

FIG. 1 is a schematic view of an example sympathetic nerve ablation system 100. System 100 may include a sympathetic nerve ablation device 120. Sympathetic nerve ablation device 120 may be used to ablate nerves (e.g., renal nerves) disposed adjacent to the kidney K (e.g., renal nerves disposed about a renal artery RA). In use, sympathetic nerve ablation device 120 may be advanced through a blood vessel such as the aorta A to a position within the renal artery RA. This may include advancing sympathetic nerve ablation device 120 through a guide sheath or catheter 14. When positioned as desired, sympathetic nerve ablation device 120 may be activated to activate one or more electrodes (not shown). This may include operatively coupling sympathetic nerve ablation device 120 to a control unit 110, which may include an RF generator, so as to supply the desired activation energy to the electrodes. For example, sympathetic nerve ablation device 120 may include a wire or conductive member 18 with a first connector 20 that can be connected to a second connector 22 on the control unit 110 and/or a wire 24 coupled to the control unit 110. In at least some embodiments, the control unit 110 may also be utilized to supply/receive the appropriate electrical energy and/or signal to activate one or more sensors disposed at or near a distal end of sympathetic nerve ablation device 120. When suitably activated, the one or more electrodes may be capable of ablating tissue (e.g., sympathetic nerves) as described below and the one or more sensors may be used to detect desired physical and/or biological parameters.

In some embodiments, the sympathetic nerve ablation device 120 may include an elongate tubular member or catheter shaft 122, as shown in FIG. 2. In some embodiments, the elongate tubular member or catheter shaft 122 may be configured to be slidingly advanced over a guidewire or other elongate medical device to a target site. In some embodiments, the elongate tubular member or catheter shaft 122 may be configured to be slidingly advanced within a guide sheath or catheter 14 to a target site. In some embodiments, the elongate tubular member or catheter shaft 122 may be configured to be advanced to a target site over a guidewire, within a guide sheath or catheter 14, or a combination thereof. An expandable member 130 may be disposed at, on, about, or near a distal region of the elongate tubular member or catheter shaft 122. In some embodiments, the expandable member 130 may be a compliant or a non-compliant balloon. In some embodiments, the expandable member 130 may be capable of shifting between an unexpanded configuration and an expanded configuration.

For example, as shown in FIG. 2, in some embodiments, one or more electrode assemblies may be arranged on the expandable member 130, shown in an expanded state, according to a plurality of generally cylindrical treatment zones A-D. In other embodiments, the expandable member 130 or other components of the treatment system may include additional electrode assemblies that are not in a treatment zone or are otherwise not used or configured to deliver a treatment energy.

The treatment zones A-D and associated electrode assemblies 140 a-d are further illustrated in FIG. 3, which is an “unrolled” depiction of a portion of the expandable member 130 of FIG. 2. The treatment zones A-D may be longitudinally adjacent to one another along longitudinal axis L-L, and may be configured such that energy applied by the electrode assemblies create treatments that may or may not overlap. Treatments applied by the longitudinally adjacent bipolar electrode assemblies 140 a-d may be circumferentially non-continuous along longitudinal axis L-L. For example, with reference to FIG. 3, lesions created in treatment zone A may in some embodiments minimize overlap about a circumference (laterally with respect to L-L in this view) with lesions created in treatment zone B. In other embodiments, however, the energy applied by the electrode assemblies, such as the electrode assemblies shown in FIG. 3, may overlap, longitudinally, circumferentially, and/or in other ways, to at least some extent. Each electrode pad assembly may include four elements, which are a distal electrode pad 150 a-d, intermediate tail 160 a-d, proximal electrode pad 170 a-d, and proximal tail 180 b,d (not shown for electrode pad assemblies 140 a and 140 c).

An exemplary electrode assembly is shown in FIGS. 4-6. FIG. 4 shows a bottom view of the example electrode assembly 200, or a view of a bottom side of the electrode assembly 200 that may face, may be in contact with, and/or may be attached and/or bonded directly to an outer surface of the expandable member 130. The electrode assembly 200 may be constructed as a flexible circuit having a plurality of layers. Such layers may be continuous or non-contiguous (i.e., made up of discrete portions). As shown in cross-section in FIG. 5, a base layer 202 of insulation may provide a foundation for the electrode assembly 200. The base layer 202 may be constructed from a polymer such as polyimide, although other materials are contemplated. In some embodiments, the base layer 202 may be about 0.010 mm to about 0.020 mm thick. In some embodiments, the base layer 202 may be about 0.015 mm thick. Other suitable thicknesses are also contemplated. For reference, the base layer 202 may form the bottom side of the electrode assembly 200 that may face, may be in contact with, and/or may be attached and/or bonded directly to the outer surface of the expandable member 130. FIG. 5 is a cross-sectional view taken along line 5-5 of FIG. 4 with the bottom side of the electrode assembly 200 facing an outer surface of the expandable member 130 and attached and/or bonded thereto. FIG. 6 is an exploded view of the electrode assembly 200 shown in FIG. 4, further illustrating the layers of the electrode assembly 200.

A conductive layer 204 may include a plurality of discrete conductive traces layered on top of the base layer 202. In some embodiments, the plurality of discrete conductive traces may be separated laterally by a non-conductive material, such as portions of the insulating layer 206. The plurality of discrete conductive traces of the conductive layer 204 may include, for example, a layer of electrodeposited copper or rolled-annealed copper. Other suitable conductive materials are also contemplated, such as grapheme and other carbon-based materials. In some embodiments, the conductive layer 204 and/or the plurality of discrete conductive traces may be about 0.010 mm to about 0.030 mm thick. In some embodiments, the conductive layer 204 and/or the plurality of discrete conductive traces may be about 0.018 mm thick. Other suitable thicknesses are also contemplated.

An insulating layer 206 may be discretely or continuously layered on top of the conductive layer 204, such that the conductive layer 204 may be fluidly sealed between the base layer 202 and the insulating layer 206. In other words, the insulating layer 206 may form a top side or surface of the electrode assembly 200 that may face away from the outer surface of the expandable member 130. The relationship between the base layer 202, the conductive layer 204, and the insulating layer 206 is illustrative, and other constructions are contemplated. Like the base layer 202, the insulating layer 206 may be constructed from a polymer such as polyimide, although other materials are contemplated. In some embodiments, the insulating layer 206 may be from about 0.010 mm thick to about 0.020 mm thick. In some embodiments, the insulating layer 206 may be about 0.013 mm thick. Other suitable thicknesses are also contemplated. In some embodiments, the insulating layer 206 may be a complete or partial polymer coating, such as PTFE or silicone. Other materials are also contemplated.

In some embodiments, the plurality of layers (i.e., the base layer 202, the conductive layer 204, and the insulating layer 206) may combine to define a thickness of the flexible circuit. In some embodiments, the thickness of the flexible circuit may be substantially constant over the length of the flexible circuit and/or the electrode assembly 200. In some embodiments, the thickness of the flexible circuit may be about 0.046 mm.

The electrode assembly 200 shown in FIG. 4 may include a distal electrode pad 208. In this region, the base layer 202 may form a rectangular shape. This is not intended to be limiting. Other shapes are contemplated. As shown, the electrode assembly 200 may include a plurality of openings extending therethrough to provide for added flexibility, and the pads and other portions of the assemblies may include rounded or curved corners, transitions and other portions. In some instances, the openings and rounded/curved features may enhance the assembly's resistance to delamination from the expandable member 130, as may occur, in some instances, when the expandable member 130 is repeatedly expanded and collapsed (which may also entail deployment from and withdrawal into a protective sheath), such as may be needed when multiple sites are treated during a procedure.

As discussed above, the distal electrode pad 208 may include a plurality of discrete conductive traces layered on top of the base layer 202. The plurality of discrete conductive traces may include a ground electrode trace 210, an active electrode trace 212, and a sensor trace 214. The ground electrode trace 210 may include an elongated ground electrode support 216 laterally offset from a sensor ground pad 218. The sensor ground pad 218 may be electrically coupled to the elongated ground electrode support 216 of the ground electrode trace 210 and may be centrally located on the distal electrode pad 208. A bridge 220 may connect a distalmost portion of the sensor ground pad 218 to a distal portion of the elongated ground electrode support 216 of the ground electrode trace 210. The bridge 220 may taper down in width as it travels to the sensor ground pad 218. In some embodiments, the bridge 220 may have a relatively uniform and thin width to enable a desired amount of flexibility. The elongated ground electrode support 216 may taper down in width at its proximal end, however, this is not required. In some embodiments, the elongated ground electrode support 216 may abruptly transition to a much thinner trace at its proximal portion, to enable a desired amount of flexibility. The active electrode trace 212 may include an elongated active electrode support 217 laterally offset from the elongated ground electrode support 216, the sensor ground pad 218, and/or a sensor power pad 224. The sensor power pad 224 may be electrically coupled to the sensor trace 214 and may be centrally located on the distal electrode pad 208. The elongated active electrode support 217 may taper down in width at its proximal end, however, this is not required. In some embodiments, the elongated active electrode support 217 may abruptly transition to a much thinner trace at its proximal portion, to enable a desired amount of flexibility. Generally, the curvature of the traces where necking is shown may be optimized to reduce balloon recapture forces and to reduce the potential for any snagging that sharper contours may present. The shape and position of the traces may also be optimized to provide dimensional stability to the electrode assembly 200 as a whole, so as to prevent distortion during deployment and use.

As shown in FIG. 4, the ground electrode trace 210 and active electrode trace 212 may each include a plurality of electrodes 222. In some embodiments, at least one electrode may be provided for each electrode trace, however, more or less may be used. For example, in some embodiments, three electrodes may be provided for each electrode trace. The plurality of electrodes 222 may protrude above and/or extend through the insulating layer 206. In some embodiments, the plurality of electrodes 222 may include at least one active electrode and at least one ground electrode attached and/or electrically connected to the elongated active electrode support 217 and the elongated ground electrode support 216, respectively. In some embodiments, a plurality of electrodes 222 may be attached and/or electrically connected to the elongated ground electrode support 216, thereby defining a plurality of ground electrodes, and/or the elongated active electrode support 217, thereby defining a plurality of active electrodes. In some embodiments, openings or cavities may be formed through the insulating layer 206 (e.g., laser ablated) down to the elongated ground electrode support 216 and/or the elongated active electrode support 217 to expose portions of the ground electrode support 216 and/or the elongated active electrode support 217 and then an electrically conductive substance, such as gold, may be electroplated into the formed openings or cavities to form the electrodes 222.

In some embodiments, the plurality of electrodes 222 may be from about 0.030 mm thick to about 0.070 mm thick. In some embodiments, the plurality of electrodes 222 may be about 0.051 mm thick. In some embodiments, the plurality of electrodes 222 may extend about 0.020 mm to about 0.050 mm above the insulating layer 206. In some embodiments, the plurality of electrodes 222 may extend about 0.038 mm above the insulating layer 206. Additionally, each electrode may have radiused corners to reduce tendency to snag, creating catch points, on other devices and/or tissue. Although the above description of the plurality of electrodes and the traces associated with them has been described in the context of a bi-polar electrode assembly, those of skill in the art will recognize that the same electrode assembly may function in a monopolar mode as well. For instance, as one non-limiting example, the plurality of electrodes associated with active electrode traces 212 and 242 may be used as monopolar electrodes, with ground electrode trace 210 disconnected during energization of those electrodes.

The sensor trace 214 may be centrally located on the distal electrode pad 208 and may include a sensor power pad 224 facing and/or adjacent the sensor ground pad 218. These pads may connect to power and ground poles of a temperature sensor 226, such as a thermistor. In some embodiments, the temperature sensor 226 may be proximally connected to the sensor power pad 224 and may be distally connected to the sensor ground pad 218. In some embodiments, the temperature sensor 226 may be in direct contact with the sensor power pad 224 and/or the sensor ground pad 218. In some embodiments, the temperature sensor 226 may be attached and/or electrically connected to the sensor power pad 224 and/or the sensor ground pad 218 by soldering, welding, and the like, or other suitable means. In some embodiments, the temperature sensor 226 may be disposed or positioned between at least one active electrode and at least one ground electrode. In some embodiments, the temperature sensor 226 may be disposed or positioned between the plurality of active electrodes and the plurality of ground electrodes.

In some embodiments, the temperature sensor 226 may have a length of about 0.500 mm to about 2.000 mm, and a width of about 0.200 mm to about 0.800 mm. In some embodiments, the temperature sensor 226 may have a length of about 1.000 mm and a width of about 0.500 mm. To help reduce overall thickness, the temperature sensor 226 may be positioned within an opening in the base layer 202. In some embodiments, the temperature sensor 226 may protrude outwardly from the base layer 202 by about 0.050 mm to about 0.200 mm. In some embodiments, the temperature sensor 226 may have a thickness of about 0.115 mm and may protrude outwardly from the base layer 202 by about 0.100 mm. In some embodiments, an overall thickness of the electrode assembly 200 at the temperature sensor 226 (i.e., including the plurality of layers and the temperature sensor 226) may be about 0.146 mm. In some embodiments, the temperature sensor 226 may comprise more than 65% of the overall thickness of the electrode assembly 200 at the temperature sensor 226.

In some embodiments, a maximum thickness of the electrode assembly 200 (including the plurality of layers, the temperature sensor 226, and the plurality of electrodes 222) may be from about 0.150 mm to about 0.200 mm. In some embodiments, the maximum thickness of the electrode assembly 200 may be about 0.184 mm. In some embodiments, the temperature sensor 226 may comprise more than 50% of the maximum thickness of the electrode assembly 200.

In some embodiments, the temperature sensor 226 may be a thermistor. As shown, the temperature sensor 226 may be disposed on a non-tissue contacting side (i.e., bottom side) of the distal electrode pad 208 and/or the electrode assembly 200. Accordingly, the temperature sensor 226 may be captured between the electrode assembly 200 and the expandable member 130 when incorporated into an ablation device 120. This may be advantageous since surface-mounted electrical components, like thermistors, may typically have sharp edges and corners, which may get caught on tissue and possibly cause problems in balloon deployment and/or retraction. This arrangement may also keep soldered connections from making contact with blood, since solder is typically non-biocompatible. Further, due to the placement of the temperature sensor 226 between the plurality of active electrodes contacting the elongated active electrode support 217 and the plurality of ground electrodes contacting the elongated ground electrode support 216, the temperature sensor 226 may measure temperature representative of the plurality of electrodes 222 and/or tissue adjacent to and/or in contact with the plurality of electrodes 222.

In other embodiments the temperature sensor 226 may be a thermocouple, such as that disclosed in U.S. Provisional App. No. 61/895,788 filed on Oct. 25, 2013, entitled “EMBEDDED THERMOCOUPLE IN DENERVATION FLEX CIRCUIT”, incorporated herein by reference in its entirety. For example, the sensor trace 214 may be centrally located on the distal electrode pad 208 and may be electrically-connected to the sensor ground pad 218 to form a temperature sensor 226, such as a thermocouple (for example, Type T configuration: Copper/Constantan). A thermocouple may generate a voltage differential at the junction of two dissimilar metals based upon the temperature at the junction, as is known in the art. In such an embodiment, an isothermal junction may be formed at a proximal end of the electrode assembly 200, spaced apart from and thermally isolated from the electrode pad(s) and/or the plurality of electrodes. The sensor ground pad 218 may be formed as a discrete trace of electrodeposited copper within the conductive layer 204, as discussed above. In such an embodiment, the distal end portion of the sensor trace 214, and in some cases the entire sensor trace 214 may be formed from, for example, constantan (i.e., copper-nickel alloy), nickel-chromium, or other suitable conductive material. The temperature sensor 226 may be formed by a distal end portion of the sensor trace 214 overlapping the sensor ground pad 218, such that the sensor trace 214 and the sensor ground pad 218 are in direct contact. In some instances, the temperature sensor 226 may be formed by sputtering the distal end portion of the sensor trace 214 over the sensor ground pad 218, thereby forming a sputtered thermocouple, or other suitable means.

In such an embodiment, the temperature sensor 226 may be embedded between the base layer 202 and the insulating layer 206, such that the temperature sensor 226 is fluidly sealed within the flexible circuit and/or the electrode assembly 200. In other words, in some embodiments, the temperature sensor 226 may not be positioned on an outer surface of the electrode assembly 200, whereas the temperature sensor 226 (thermistor) shown in FIGS. 4-6 is positioned on or extending outwardly from the outer surface of the electrode assembly 200. In some embodiments, no protrusion may be formed on the bottom side of the electrode assembly 200 at the temperature sensor 226. For example, in a flattened configuration, the bottom side of the electrode assembly 200 that faces the outer surface of the expandable member 130 may form an uninterrupted surface. In some embodiments, in a flattened configuration, the bottom side of the electrode assembly may include (and/or the uninterrupted surface may form) an essentially continuously planar surface with the temperature sensor 226 in place on/in the electrode assembly 200. In other words, the temperature sensor 226 may not protrude or extend outwardly through or from the base layer 202.

Moving proximally from the distal electrode pad 208, the combined base layer 202, conductive layer 204, and insulating layer 206 may reduce in lateral width to an intermediate tail 228. Here, as shown in FIG. 4, the conductive layer 204 may be formed to include an intermediate ground line 230, intermediate active electrode line 232, and intermediate sensor line 234, which may be respectively coextensive traces of the ground electrode trace 210, active electrode trace 212, and sensor trace 214 of the distal electrode pad 208.

Continuing to move proximally from the intermediate tail 228, the combined base layer 202, conductive layer 204, and insulating layer 206 may increase in lateral width to form a proximal electrode pad 236. The proximal electrode pad 236 may be constructed similarly to the distal electrode pad 208, with the electrode geometry and temperature sensor arrangement being essentially identical, although various differences may be present. However, as shown, the proximal electrode pad 236 may be laterally offset from the distal electrode pad 208 with respect to a central longitudinal axis G-G extending along the intermediate ground line 230. The intermediate active electrode line 232 and intermediate sensor line 234 may be laterally coextensive with the proximal electrode pad 236 on parallel respective axes with respect to central axis G-G.

From the proximal electrode pad 236, the combined base layer 202, conductive layer 204, and insulating layer 206 may reduce in lateral width to form a proximal tail 238. The proximal tail 238 may include a proximal ground line 240, proximal active electrode line 242, and proximal sensor line 244, as well as the intermediate active electrode line 232 and intermediate sensor line 234. The proximal tail 238 may include connectors (not shown) to enable coupling to one or more sub-wiring harnesses and/or connectors and ultimately to control unit 110, such as via wire or conductive member 18 (shown in FIG. 1). Each of these lines may be extended along parallel respective axes with respect to central axis G-G.

As shown, the electrode assembly 200 may have an asymmetric arrangement of the distal electrode pad 208 and proximal electrode pad 236, about central axis G-G. Further, the ground electrodes of both electrode pads may be substantially aligned along central axis G-G, along with the intermediate and proximal ground lines 230/240. It has been found that this arrangement may present certain advantages. For example, by essentially sharing the same ground trace, the width of the proximal tail may be only about one and a half times that of the intermediate tail 228, rather than being approximately twice as wide if each electrode pad had independent ground lines. Thus, the proximal tail 238 may be narrower than two intermediate tails 228 positioned side-by-side.

In some embodiments, the electrode assembly(s) 200 may be substantially linear, extending along or at an angle to the longitudinal axis L-L along the entire length of the expandable member 130. In some embodiments, the electrode assemblies may extend parallel to the longitudinal axis in a proximal region, and then be bent into an angled orientation in a distal region (not shown).

The use of medical devices that include a balloon with one or more electrode assemblies coupled thereto, for example as described herein, may be desirable. In some instances, however, the electrode assemblies may include relatively stiff and/or bulky materials or elements. Accordingly, when the balloon is deflated following a treatment procedure, the electrode assembly may tend to flatten and/or widen out. When so configured, the one or more electrode assemblies, and/or components or edges thereof, might catch on the edge of a guide catheter when proximally refracting the medical device (e.g., including the affixed electrode assemblies) into the guide catheter. Disclosed herein are medical devices that include structural features that may reduce the likelihood of an electrode assembly or other structures of the medical device tearing in the event the electrode assembly catches on the end of a guide catheter (or other device) when being refracted, for example, into the guide catheter.

FIG. 7 illustrates a first embodiment of a reinforcement layer 300 of a flexible circuit of an electrode assembly 200, as described herein, mounted on the expandable member 130 (e.g., inflatable balloon). The reinforcement layer 300 may be one of a plurality of layers of the flexible circuit of the electrode assembly 200. For example, the reinforcement layer 300 may be the insulating base layer 202, the insulating layer 206, and/or an additional layer of the flexible circuit.

The reinforcement layer 300 may be formed from a polymeric material having oriented, or biaxially oriented, polymer chains 310. For example, the polymeric material may have polymer chains 310 generally oriented perpendicular to the longitudinal axis L of the expandable member 130 and catheter shaft 122. Such an orientation of the polymer chains 310 may increase the tear resistance of the reinforcement layer 300 in a direction parallel to the longitudinal axis L. Some suitable materials for the reinforcement layer 300 include a uniaxially or biaxially oriented polyimide (PI) or polyethylene terephthalate (PET) sheet of material, although other polymeric materials may be used, if desired.

In some instances, the base layer 202 and the insulating layer 206 may include oriented polymer chains 310. In such instances, the oriented polymer chains 310 of the base layer 202 may be arranged perpendicular to the oriented polymer chains 310 of the insulating layer 206. Thus, the electrode assembly 200 may be mounted to the expandable member 130 with the oriented polymer chains 310 of the base layer 202 arranged generally perpendicular to the longitudinal axis L, or the electrode assembly 200 may be mounted to the expandable member 130 with the oriented polymer chains 310 of the insulating layer 206 arranged generally perpendicular to the longitudinal axis L.

In other instances, the base layer 202 and the insulating layer 206 may include oriented polymer chains 310 with the oriented polymer chains 310 of the base layer 202 arranged parallel to the oriented polymer chains 310 of the insulating layer 206. Thus, the electrode assembly 200 may be mounted to the expandable member 130 with the oriented polymer chains 310 arranged generally perpendicular to the longitudinal axis L.

FIGS. 8A and 8B illustrate additional embodiments of a reinforcement layer 400 of a flexible circuit of an electrode assembly 200, as described herein, mounted on the expandable member 130 (e.g., inflatable balloon). The reinforcement layer 400 may be one of a plurality of layers of the flexible circuit of the electrode assembly 200. For example, the reinforcement layer 400 may be the insulating base layer 202, the insulating layer 206, and/or an additional layer of the flexible circuit.

The reinforcement layer 400 may be formed from a polymeric material including one or more, or a plurality of reinforcement fibers 410 embedded therein. For example, in some instances the reinforcement fibers 410 may be ultra-high molecular weight polyethylene (UHMWPE) fibers (e.g., Dyneema®), nanotube fibers, such as double-walled nanotube (DWNT) polymer fibers, carbon nanotube fibers, glass fibers, poly-paraphenylene terephthalamide (e.g., Kevlar®) filaments, etc. Other suitable materials include natural materials such as cotton, wool or cellulose, for example. In some embodiments, the reinforcement fibers 410 may have a length of about 2-6 microns or about 3-4 microns for example. In some instances, the reinforcement fiber 410 may be a continuous fiber such as a nanofiber formed during an electro-spinning process. In some instances, the reinforcement layer 400 may include a continuous fiber 410 or a plurality of continuous fibers 410 formed using an electro-spinning process to deposit a continuous bundle of nanofibers on the reinforcement layer 400.

The reinforcement fibers 410 may be randomly arranged in the polymeric sheet of material of the reinforcement layer 400 as shown in FIG. 8B, or the reinforcement fibers 410 may be arranged in a desired orientation. For example, in some instances, the reinforcement fibers 410 may be arranged generally perpendicular to the longitudinal axis L of the expandable member 130 and catheter shaft 122 as shown in FIG. 8A.

In some instances the reinforcement layer 400 may be formed of a polyimide (PI) or polyethylene terephthalate (PET) sheet of material, with the reinforcement fibers 410 embedded therein.

FIG. 9 illustrates another embodiment of a reinforcement layer 500 of a flexible circuit of an electrode assembly 200, as described herein, mounted on the expandable member 130 (e.g., inflatable balloon). The reinforcement layer 500 may be one of a plurality of layers of the flexible circuit of the electrode assembly 200. For example, the reinforcement layer 500 may be the insulating base layer 202, the insulating layer 206, and/or an additional layer of the flexible circuit.

The reinforcement layer 500 may be formed from a polymeric material including reinforcement fibers 510 embedded therein. For example, the reinforcement layer 500 may be formed of a polyimide (PI) or polyethylene terephthalate (PET) sheet of material, with the reinforcement fibers 510 embedded therein. In the embodiment of FIG. 9, the reinforcement fibers 510 are illustrated as extending continuously across the entire width of the reinforcement layer 500 from a first edge to a second edge of the reinforcement layer 500. However, in other instances, the reinforcement fibers 510 may be discontinuously arranged across less than the entire width of the reinforcement layer 500.

The reinforcement fibers 510 may be arranged in a desired orientation, or the reinforcement fibers 510 may be randomly arranged in the polymeric sheet of material of the reinforcement layer 500. For example, as shown in FIG. 9, the reinforcement fibers 510 may be arranged generally perpendicular to the longitudinal axis L of the expandable member 130 and catheter shaft 122.

FIG. 10 illustrates another embodiment of a reinforcement layer 600 of a flexible circuit of an electrode assembly 200, as described herein, mounted on the expandable member 130 (e.g., inflatable balloon). The reinforcement layer 600 may be one of a plurality of layers of the flexible circuit of the electrode assembly 200. For example, the reinforcement layer 600 may be the insulating base layer 202, the insulating layer 206, and/or an additional layer of the flexible circuit.

The reinforcement layer 600 may be formed from a polymeric material including reinforcement fibers 610 embedded therein. For example, the reinforcement layer 600 may be formed of a polyimide (PI) or polyethylene terephthalate (PET) sheet of material, with the reinforcement fibers 610 embedded therein. The reinforcement fibers 610 may have an outer diameter that tapers from a first end of a reinforcement fiber 610 to a second end of a reinforcement fiber 610. The tapered outer diameters of the reinforcement fibers 610 may create a mechanical lock with the polymeric sheet of material to prevent the reinforcement fibers 610 from being pulled out of the polymeric sheet of material of the reinforcement layer 600.

The reinforcement fibers 610 may be arranged in a desired orientation, or the reinforcement fibers 610 may be randomly arranged in the polymeric sheet of material of the reinforcement layer 600. For example, as shown in FIG. 10, the reinforcement fibers 610 may be arranged generally perpendicular to the longitudinal axis L of the expandable member 130 and catheter shaft 122 with alternating tapered outer diameters.

FIG. 11 illustrates another embodiment of a reinforcement layer 700 of a flexible circuit of an electrode assembly 200, as described herein, mounted on the expandable member 130 (e.g., inflatable balloon). The reinforcement layer 700 may be one of a plurality of layers of the flexible circuit of the electrode assembly 200. For example, as shown in FIG. 11, the reinforcement layer 700 may be interposed between the base layer 202 and the insulating layer 206. However, in other instances, the reinforcement layer 700 may be the insulating base layer 202 or the insulating layer 206.

The reinforcement layer 700 may be a microfabric layer, such as a woven, knitted, braided or otherwise formed mesh of filaments. In some instances, the reinforcement layer 700 may be a microfabric layer formed as a woven mesh of polyimide and/or polyethylene terephthalate (PET) fibers. Other suitable materials include natural materials such as cotton, wool or cellulose, for example. In some instances, the reinforcement layer 700 may include a continuous fiber such as a nanofiber formed during an electro-spinning process formed into a fabric or mesh, for example. In some instances, the reinforcement layer 700 may be a microfabric mesh including a continuous fiber 410 or a plurality of continuous fibers 410 formed using an electro-spinning process to deposit a continuous bundle of nanofibers on the reinforcement layer 700.

As shown in FIG. 11, in some instances the reinforcement layer 700 (e.g., a microfabric layer) may include a first opening such that a first electrode 222 may extend through the first opening in electrical contact with a first conductive trace (e.g., the electrode support 216 of the ground electrode trace 210) of the flexible circuit, and the reinforcement layer 700 (e.g., a microfabric layer) may include a second opening such that a second electrode 222 may extend through the second opening in electrical contact with a second conductive trace (e.g., the elongated active electrode support 217 of the active electrode trace 212) of the flexible circuit. The reinforcement layer 700 may include an additional opening for each additional electrode 222 of the flexible circuit of the electrode assembly 200.

In other embodiments, the reinforcement layer 700 may be positioned on the other side of the electrode support 216 of the ground electrode trace 210, the elongated active electrode support 217 of the active electrode trace 212, and the sensor ground pad 218 of the flexible circuit. Thus, the reinforcement layer 700 may be positioned between the electrode traces and the insulating layer 202. Accordingly, the reinforcement layer 700 may include openings to permit the temperature sensor 226 to electrically contact the sensor ground pad 218 through the reinforcement layer 700.

In some instances, the openings in the reinforcement layer 700 may be pre-formed in the reinforcement layer 700 prior to being applied to the flexible circuit. In other instances, the openings may be cut through the reinforcement layer 700 such as during a laser ablation process during the manufacture of the flexible circuit.

In other instances, the base layer 202, the insulating layer 206, and/or an additional layer may be a thermoplastic polyamide, such as Ultramid®, which in some instances may be a glass reinforced polyamide.

In accordance with this disclosure, the inclusion of a reinforcement structure with one or more of the layers of the electrode assemblies 200 may provide the electrode assemblies 200 with enhanced tear resistance properties. For example, the reinforcement layer of the flexible circuit may have an initial tear strength of greater than 7.5 N (1.7 lbf) according to ASTM D-1004-09 and a tear propagation strength of greater than 0.15 N (0.03 lbf) according to ASTM D-1922-09. In some instances, the initial tear strength of the reinforcement layer may be greater than 8.0 N (1.8 lbf) according to ASTM D-1004-09 and/or the tear propagation strength may be greater than 0.2 N (0.045 lbf) according to ASTM D-1922-09.

In use, the ablation device 120 may be advanced through a blood vessel or body passageway to a position adjacent to a target tissue (e.g., within a renal artery), in some cases with the aid of a delivery sheath or catheter 14. In some embodiments, the target tissue may be one or more sympathetic nerves disposed about the blood vessel. In some embodiments, the control unit 110 may be operationally coupled to the ablation device 120, which may be inserted into a blood vessel or body passageway such that an expandable member 130 (having a plurality of electrode assemblies 200) may be placed adjacent to the target tissue where therapy is required. Placement of the ablation device 120 adjacent the target tissue where therapy is required may be performed according to conventional methods, (e.g., over a guidewire under fluoroscopic guidance). When suitably positioned, the expandable member 130 may be expanded from a collapsed delivery configuration to an expanded configuration, for example by pressurizing fluid from about 2-10 atm in the case of a balloon. This may place/urge the plurality of electrodes against the wall of the blood vessel. The plurality of active electrodes may be activated. Ablation energy may be transmitted from the plurality of active electrodes through the target tissue (where sympathetic nerves may be ablated, modulated, or otherwise impacted), and back through the plurality of ground electrodes, in a bipolar configuration, or back through the common ground electrode, in a monopolar configuration. Following treatment, the expandable member 130 may be collapsed to the collapsed delivery configuration for retraction into the guide sheath or catheter 14 and subsequent withdrawal from the blood vessel or body passageway.

The materials that can be used for the various components of the ablation device 120 (and/or other devices disclosed herein) may include those commonly associated with medical devices. For simplicity purposes, the following discussion makes reference to the ablation device 120. However, this is not intended to limit the devices and methods described herein, as the discussion may be applied to other similar tubular members and/or expandable members and/or components of tubular members and/or expandable members disclosed herein.

The ablation device 120 and the various components thereof may be made from a metal, metal alloy, polymer (some examples of which are disclosed below), a metal-polymer composite, ceramics, combinations thereof, and the like, or other suitable material. Some examples of suitable polymers may include polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), polyoxymethylene (POM, for example, DELRIN® available from DuPont), polyether block ester, polyurethane (for example, Polyurethane 85A), polypropylene (PP), polyvinylchloride (PVC), polyether-ester (for example, ARNITEL® available from DSM Engineering Plastics), ether or ester based copolymers (for example, butylene/poly(alkylene ether) phthalate and/or other polyester elastomers such as HYTREL® available from DuPont), polyamide (for example, DURETHAN® available from Bayer or CRISTAMID® available from Elf Atochem), elastomeric polyamides, block polyamide/ethers, polyether block amide (PEBA, for example available under the trade name PEBAX®), ethylene vinyl acetate copolymers (EVA), silicones, polyethylene (PE), Marlex high-density polyethylene, Marlex low-density polyethylene, linear low density polyethylene (for example REXELL®), polyester, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polytrimethylene terephthalate, polyethylene naphthalate (PEN), polyetheretherketone (PEEK), polyimide (PI), polyetherimide (PEI), polyphenylene sulfide (PPS), polyphenylene oxide (PPO), poly paraphenylene terephthalamide (for example, KEVLAR®), polysulfone, nylon, nylon-12 (such as GRILAMID® available from EMS American Grilon), perfluoro(propyl vinyl ether) (PFA), ethylene vinyl alcohol, polyolefin, polystyrene, epoxy, polyvinylidene chloride (PVdC), poly(styrene-b-isobutylene-b-styrene) (for example, SIBS and/or SIBS 50A), polycarbonates, ionomers, biocompatible polymers, other suitable materials, or mixtures, combinations, copolymers thereof, polymer/metal composites, and the like. In some embodiments the sheath can be blended with a liquid crystal polymer (LCP). For example, the mixture can contain up to about 6 percent LCP.

Some examples of suitable metals and metal alloys include stainless steel, such as 304V, 304L, and 316LV stainless steel; mild steel; nickel-titanium alloy such as linear-elastic and/or super-elastic nitinol; other nickel alloys such as nickel-chromium-molybdenum alloys (e.g., UNS: N06625 such as INCONEL® 625, UNS: N06022 such as HASTELLOY® C-22®, UNS: N10276 such as HASTELLOY® C276®, other HASTELLOY® alloys, and the like), nickel-copper alloys (e.g., UNS: N04400 such as MONEL® 400, NICKELVAC® 400, NICORROS® 400, and the like), nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such as MP35-N® and the like), nickel-molybdenum alloys (e.g., UNS: N10665 such as HASTELLOY® ALLOY B2®), other nickel-chromium alloys, other nickel-molybdenum alloys, other nickel-cobalt alloys, other nickel-iron alloys, other nickel-copper alloys, other nickel-tungsten or tungsten alloys, and the like; cobalt-chromium alloys; cobalt-chromium-molybdenum alloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like); platinum enriched stainless steel; titanium; combinations thereof; and the like; or any other suitable material.

As alluded to herein, within the family of commercially available nickel-titanium or nitinol alloys, is a category designated “linear elastic” or “non-super-elastic” which, although may be similar in chemistry to conventional shape memory and super elastic varieties, may exhibit distinct and useful mechanical properties. Linear elastic and/or non-super-elastic nitinol may be distinguished from super elastic nitinol in that the linear elastic and/or non-super-elastic nitinol does not display a substantial “superelastic plateau” or “flag region” in its stress/strain curve like super elastic nitinol does. Instead, in the linear elastic and/or non-super-elastic nitinol, as recoverable strain increases, the stress continues to increase in a substantially linear, or a somewhat, but not necessarily entirely linear relationship until plastic deformation begins or at least in a relationship that is more linear that the super elastic plateau and/or flag region that may be seen with super elastic nitinol. Thus, for the purposes of this disclosure linear elastic and/or non-super-elastic nitinol may also be termed “substantially” linear elastic and/or non-super-elastic nitinol.

In some cases, linear elastic and/or non-super-elastic nitinol may also be distinguishable from super elastic nitinol in that linear elastic and/or non-super-elastic nitinol may accept up to about 2-5% strain while remaining substantially elastic (e.g., before plastically deforming) whereas super elastic nitinol may accept up to about 8% strain before plastically deforming. Both of these materials can be distinguished from other linear elastic materials such as stainless steel (that can also can be distinguished based on its composition), which may accept only about 0.2 to 0.44 percent strain before plastically deforming.

In some embodiments, the linear elastic and/or non-super-elastic nickel-titanium alloy is an alloy that does not show any martensite/austenite phase changes that are detectable by differential scanning calorimetry (DSC) and dynamic metal thermal analysis (DMTA) analysis over a large temperature range. For example, in some embodiments, there may be no martensite/austenite phase changes detectable by DSC and DMTA analysis in the range of about −60 degrees Celsius (° C.) to about 120° C. in the linear elastic and/or non-super-elastic nickel-titanium alloy. The mechanical bending properties of such material may therefore be generally inert to the effect of temperature over this very broad range of temperature. In some embodiments, the mechanical bending properties of the linear elastic and/or non-super-elastic nickel-titanium alloy at ambient or room temperature are substantially the same as the mechanical properties at body temperature, for example, in that they do not display a super-elastic plateau and/or flag region. In other words, across a broad temperature range, the linear elastic and/or non-super-elastic nickel-titanium alloy maintains its linear elastic and/or non-super-elastic characteristics and/or properties.

In some embodiments, the linear elastic and/or non-super-elastic nickel-titanium alloy may be in the range of about 50 to about 60 weight percent nickel, with the remainder being essentially titanium. In some embodiments, the composition is in the range of about 54 to about 57 weight percent nickel. One example of a suitable nickel-titanium alloy is FHP-NT alloy commercially available from Furukawa Techno Material Co. of Kanagawa, Japan. Some examples of nickel titanium alloys are disclosed in U.S. Pat. Nos. 5,238,004 and 6,508,803, which are incorporated herein by reference. Other suitable materials may include ULTANIUM™ (available from Neo-Metrics) and GUM METAL™ (available from Toyota). In some other embodiments, a superelastic alloy, for example a superelastic nitinol can be used to achieve desired properties.

In at least some embodiments, portions of the ablation device 120 may also be doped with, made of, or otherwise include a radiopaque material. Radiopaque materials are understood to be materials capable of producing a relatively bright image on a fluoroscopy screen or another imaging technique during a medical procedure. This relatively bright image aids the user of the ablation device 120 in determining its location. Some examples of radiopaque materials can include, but are not limited to, gold, platinum, palladium, tantalum, tungsten alloy, polymer material loaded with a radiopaque filler, and the like. Additionally, other radiopaque marker bands and/or coils may also be incorporated into the design of the ablation device 120 to achieve the same result.

In some embodiments, a degree of Magnetic Resonance Imaging (MRI) compatibility may be imparted into the ablation device 120. For example, portions of device, may be made of a material that does not substantially distort the image and create substantial artifacts (i.e., gaps in the image). Certain ferromagnetic materials, for example, may not be suitable because they may create artifacts in an MRI image. In some of these and in other embodiments, portions of the ablation device 120 may also be made from a material that the MRI machine can image. Some materials that exhibit these characteristics include, for example, tungsten, cobalt-chromium-molybdenum alloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like), nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such as MP35-N® and the like), nitinol, and the like, and others.

U.S. patent application Ser. No. 13/750,879, filed on Jan. 25, 2013, and entitled “METHODS AND APPARATUSES FOR REMODELING TISSUE OF OR ADJACENT TO A BODY PASSAGE”, now published as U.S. Patent Publication No. US20130165926A1, is herein incorporated by reference.

It should be understood that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of steps without exceeding the scope of the disclosure. This may include, to the extent that it is appropriate, the use of any of the features of one example embodiment being used in other embodiments. The invention's scope is, of course, defined in the language in which the appended claims are expressed. 

What is claimed is:
 1. A medical device for sympathetic nerve ablation, comprising: a catheter shaft having a longitudinal axis; an expandable balloon disposed on the catheter shaft, the balloon being capable of shifting between an unexpanded configuration and an expanded configuration; and an elongate electrode assembly constructed as a flexible circuit having a plurality of layers, the electrode assembly mounted on an outer surface of the balloon, wherein the flexible circuit comprises a distal electrode pad and a tail extending proximally from the distal electrode pad; wherein a first layer of the plurality of layers of the flexible circuit has an initial tear strength of greater than 7.5 N (1.7 lbf) according to ASTM D-1004-09.
 2. The medical device of claim 1, wherein the first layer of the plurality of layers of the flexible circuit has a tear propagation strength of greater than 0.15 N (0.03 lbf) according to ASTM D-1922-09.
 3. The medical device of claim 1, wherein the first layer of the plurality of layers of the flexible circuit has a tear propagation strength of greater than 0.2 N (0.045 lbf) according to ASTM D-1922-09.
 4. The medical device of claim 1, wherein the first layer of the plurality of layers of the flexible circuit has an initial tear strength of greater than 8.0 N (1.8 lbf) according to ASTM D-1004-09.
 5. The medical device of claim 1, wherein the first layer is a first insulating layer formed of a reinforced polymeric material and the flexible circuit includes a plurality of conductive traces interposed between the first insulating layer and a second insulating layer formed of a polymeric material.
 6. The medical device of claim 5, wherein the reinforced polymeric material includes a plurality of fibers oriented generally perpendicular to the longitudinal axis of the catheter shaft.
 7. The medical device of claim 5, wherein the reinforced polymeric material includes polymeric chains oriented generally perpendicular to the longitudinal axis of the catheter shaft.
 8. The medical device of claim 7, wherein the polymeric material of the second insulating layer includes polymeric chains oriented generally parallel to the longitudinal axis of the catheter shaft.
 9. The medical device of claim 5, wherein the reinforced polymeric material includes a plurality of fibers, the plurality of fibers having tapered outer diameters.
 10. The medical device of claim 9, wherein the plurality of fibers are arranged such that adjacent fibers having alternating tapered outer diameters.
 11. The medical device of claim 1, wherein the first layer is a microfabric layer.
 12. The medical device of claim 11, wherein the microfabric layer includes a first opening and a second opening; and wherein the electrode assembly includes a first electrode extending through the first opening in electrical contact with a first conductive trace of the flexible circuit and a second electrode extending through the second opening in electrical contact with a second conductive trace of the flexible circuit.
 13. The medical device of claim 11, wherein the microfabric is a woven mesh of polyimide fibers.
 14. The medical device of claim 11, wherein the microfabric layer is positioned between a first insulating polymeric layer and a second insulating polymeric layer of the flexible circuit.
 15. The medical device of claim 1, wherein the first layer includes poly-paraphenylene terephthalamide filaments.
 16. A medical device for tissue ablation, comprising: a catheter shaft having a longitudinal axis; an expandable member coupled to the catheter shaft, the expandable member being capable of shifting between an unexpanded configuration and an expanded configuration; and an elongate electrode assembly constructed as a flexible circuit mounted on an outer surface of the expandable member; wherein the flexible circuit includes a plurality of conductive traces interposed between a first insulating layer formed of a reinforced polymeric material and a second insulating layer formed of a polymeric material; and wherein the flexible circuit comprises a distal electrode pad and a tail extending proximally from the distal electrode pad.
 17. The medical device of claim 16, wherein the reinforced polymeric material includes a plurality of fibers oriented generally perpendicular to the longitudinal axis of the catheter shaft.
 18. The medical device of claim 16, wherein the reinforced polymeric material includes polymeric chains oriented generally perpendicular to the longitudinal axis of the catheter shaft.
 19. The medical device of claim 18, when the second insulating layer includes polymeric chains oriented generally parallel to the longitudinal axis of the catheter shaft.
 20. The medical device of claim 18, wherein the second insulating layer includes polymeric chains oriented generally perpendicular to the longitudinal axis of the catheter shaft. 